1. Field of the Invention
The present invention relates to lasers and particularly to a laser-pumped, thulium-doped, solid state laser for producing a CW laser emission which is tunable over the range of wavelengths from about 1.86 microns to about 2.14 microns at or near room temperature.
2. Description of the Prior Art
The near infrared spectral region contains strong absorption bands for several important molecules. For example, the region near 2 microns contains the v.sub.2 +v.sub.3 (centered at 1.88 microns) water absorption band and the 2v.sub.1 +v.sub.3 (centered at 1.96 microns). the v.sub.1 +2v.sub.2 +v.sub.3 (centered at 2.01 microns), and the 4v.sub.2 +v.sub.3 (centered at 2.06 microns) carbon dioxide absorption bands. Therefore, tunable lasers in at least this 1.88 to 2.06 micron region are of interest for remote sensing applications (such as coherent laser radar) and for sensitive absorption techniques (such as frequency modulation spectroscopy). Such tunable lasers are also of interest in medical applications due to the strong absorption of liquid water near 1.93 microns. These tunable lasers can also be utilized in the field of high resolution spectroscopy of molecules and solid state materials.
Previous researchers have pumped the .sup.3 F.sub.4 to .sup.3 H.sub.6 transition of Tm.sup.3+ :YAG to obtain laser emissions in the area of 2 micron wavelengths. Some previous researchers have obtained pulsed emissions at 1.88 microns and at 2.01 microns at a temperature of 77.degree. K., pulsed emission at 2.02 microns at room temperature, and CW emission at a wavelength of 2.01 microns at 77.degree. K. Other researchers have achieved room-temperature, CW laser emission at 1.86 microns with krypton laser pumping in Tm.sup.3+ :YSGG.
Therefore, there is a need for a laser system to provide a room-temperature, CW laser emission that is continuously tunable over the spectral range of 1.86 to 2.14 microns for use in any of the above-identified variety of different applications.